1. Field of the Invention
The present invention relates to a route selection control system for a packet switching network, and more particularly to an alternate trunking function for a packet switching network suitable for preventing a transfer delay time of a packet in a packet switching network from increasing by occurrence of the "ping-pong phenomenon" in which the packet is repeatedly transmitted between two nodes due to a failure of a transmission path of the switching network or the like.
2. Description of the Related Art
As a conventional technique for avoiding occurrent of the ping-pong phenomenon in the packet switching network, is described in, for example, "LOGIC OF INFORMATION NETWORK" edited and written by Shoichi Noguchi et al., published by Iwanami Shoten on Jun. 10, 1982, at pages 200-209.
In this technique, a source address is provided in a packet and occurrence of the ping-pong phenomenon is suppressed by using the source address. However, even if this method is used, the ping-pong phenomenon may occur. More particularly, a packet is provided with a counter which is incremented by one each time the packet is repeated and when a count of the counter exceeds a fixed value, the packet is discarded.
The conventional technique does not take account of repeating while avoiding the route on which the ping-pong phenomenon occurs in the packet switching network. Thus, a succeeding packet is transmitted on the same route, so that the ping-pong phenomenon may occur again with high possibility. Consequently, there is a problem that a transfer delay time of the packet and the traffic in the packet switching network are increased.